Above : Chelidonum majus near the Chateau de Nidau, in the commune of Nidau just across the Thiel Canal from Biel/Bienne.
This report continues in the tradition of amateur botanists contributing useful plant observation data with modern guidebooks and smartphone applications. The surveys focus on the urban Suze river and its Madretschkanal variant in Biel/Bienne. The first part of the surveys were completed between June and September 2020 and focused on the urban Suze river and its Madretschkanal variant in Biel/Bienne. The second set of surveys were conducted between February 2021 and September 2021 and included a wider geographical scope around the municipality of Biel/Bienne. The objective was to construct an initial dataset on the remnant flowering plant populations growing in different green spaces around the city of Biel/Bienne and develop some standard reporting to make the data actionable for scientific and management purposes. In the medium term, the objective is to efficiently collect actionable data on vascular plant biodiversity in the municipality and integrate this with existing data to improve management of the ecosystem services provided by municipal spaces.
A broad range of vascular plants have been under increasing threat for some time with the following evaluation made in 2010:
Overall, every single RedList documents a manifest and sustained loss of species diversity at national level. Most threatened species appear to be bound for further losses – with no likelihood of this trend being reversed in the short term. In other words, the requirement enshrined in the Swiss Constitution that animal and plant species be prevented from going extinct has not been fulfilled.
In Switzerland the vascular plants that are most threatened, like with many other taxa, are aquatic or semi-aquatic {cite}Bornand_2016. Widespread modification of waterways, the spread of invasive species, agricultural run-off, development of shorelines and regulation of water levels has led to the decline of suitable habitats and thus some 70% of species are evaluated as threatened to some extent in the latest 2016 Redlist. Next come species associated with traditional forms of agriculture and land management that have largely disappeared over the past 100 years, namely species in low altitude prairies, ruderal areas, and cropland/vineyards, which range from 40% - 60% threatened (Ibid). The decline of these species follows directly from changing agricultural practices. The species of least concern are associated with alpine habitat, rockfalls, and other largely undisturbed habitat that have historically been relatively spared from encroachment - although for alpine habitats this is increasingly not the case as agriculture and development continue (Ibid). All of this is unfolding against the backdrop of accelerating climate change that researchers expect will provoke a major shift in habitat distributions and be a medium-term stress factor for a significant number of Switzerland's vascular plants {cite}Vittoz_2013.
Knowing that widespread local extinctions irreversibly harm the genetic base of plant populations and precede general extinctions, the thousands of local extinctions of sensitive and endangered species identified by researchers in 2020 is extremely alarming, to quote the researchers{cite}Hicks_2020:
Our study presents clear evidence that current efforts to conserve threatened plant species are insufficient to achieve national and international targets (Convention on Biological Diversity (CBD), 2011; Swiss Biodiversity Strategy 2012) for maintaining biodiversity. The current paradigm of protecting and restoring threatened habitats is failing to avert extinctions. Going forward, we need to develop a comprehensive landscape approach, involving the creation of ecological infrastructure and translocation and assisted migration of threatened species into suitable habitats.
Above : This figure taken from Infoflora's 2019 Regional Redlist shows the regional differences in the threat facing vascular plants across Switzerland's biogeographical region. We see that the middle plateau / central plateau (MP) has the highest number of plants rated as higher than "LC", or least concern.
The heart of Switzerland's population and economic output, the Central Plateau / Middle Plateau is also where these localized extinctions are most prominent. Some 60% of the vascular plant species evaluated for the IUCN's Red List in the Central Plateau are classified as potentially or actually regionally threatened and the Jura region follows with 50% {cite}Infoflora_2019. Again, species associated with freshwater habitats are the group of most concern, with some 3/4 of species under potential threat. Around 60% of the alpine populations that survive throughout the plateau, are evaluated as under potential threat, as are just over half of lowland grassland species, and nearly half of forest species {cite}Infoflora_2019. The pictureIncreased levels of output and consumption, as well as relatively intensive agricultural practices, are identified as the main drivers of risk for regional biodiversity. Not all of this is due directly to higher anthropogenic pressures: the central plateau in particular hosts many habitats for its size that includes isolated, localized populations that are inherently more vulnerable to pressures on their populations (Ibid).
A judicious use of public spaces, such as road verges, railroad berms and parks, that balances their potential as habitats with the needs and requirements of the city's inhabitants can mitigate some of the anthropologic pressure. Allowing spaces to go un-mowed, sowing native wild-flower beds, and creating micro-habitats throughout urban and suburban areas can benefit both herbaceous and predatory insects {cite}Sattler_2011. In fact, (sub)urban green spaces and road verges can provide plants, insects, and birds with suitable conditions to pursue their life cycles and even become a "last refuge" for certain species (ibid). Further, the most recent data of nationwide biodiversity provided by the Biodiversity Monitoring System shows a significant decline in urban vascular plant species {cite}FOEN_2020. While private gardens clearly provide refuge for native species, research also shows that private gardens are heavily biased towards non-native plants, making public spaces even more important as a suitable refuge for remnant wild species. As such, improvement and maintenance of areas in and around urban centers could yield outsized results in terms of biodiversity preservation at this critical juncture for the future of ecosystem services.
There are a number of different strategies that municipalities can use.to boost wildflower diversity. The two most comparable strategies that do not require a heavy modification of existing space is the sowing of wildflowers versus reduced mowing frequencies. Both allow flowers to bloom, yet one requires more inputs whereas the latter requires fewer inputs. Further, some reserach chows that plantations ofannual and perennial wildflowers do not provide resources as continuously throughout the year as the remnant weed populations of the city. Preliminary exprimental evidence from Dublin suggests that remnant and sown meadows support similar levels of pollinator diversity and this is an area of ongoing research in how to boost natural capital in urban and suburban areas through green space management.
In the first year, the focus was primarily on the urban Suze river and its Madretschkanal variant. Along this stretch of the river there are many varied habitats, ranging from deep shade to full pavement to flower strips maintained for ecological and aesthetic purposes. The sites are managed by the municipality to a greater or less degree and all areas surveyed were open access to the public and reasonably accessible for an average person. In 2021 the surveys included a wider geographic scope, but still largely remained in Biel and its environs. The zones surveyed ranged from railroad berms to green areas in and around sidewalks. As such, the sites varied greatly in size and shape. The size of the sites was not recorded, but a detailed description of is available. In nearly all cases it is also possible to recover the boundary of the sites based on the geometry of the object as surveys were usually bounded by sidewalks, roads, or other barriers.
Above : Map of survey locations around Biel/Bienne in 2020 - 2021. Note the heavy focus on the Suze river and the Madretschkanal branch, as well as the Madretch quarter of Biel/Bienne in particular.
Above : Images of three survey sites along the urban Suze river and the Madretschkanal. There was a great diversity in survey site characteristics amenable to many varieties of plants.
The data results from surveys of plants carried out between June - September 2020 and February - September 2021. A site was inspected for the vascular plants in flower, and all the different species identified were recorded. It was decided to not use transects or gridsquares and avoid estimating the relatively proportion of different plant populations. The methodology and thoroughness of the surveys changed over time as the surveyor gained experience. In June 2020, the number of plants that could be reliably identified by the surveyor was small, where as by August 2020, the surveyor could reliably identify the common species that dominate the landscape. This meant that the 2020 - 2021 observations are not directly comparable as the surveyor was able to record a significantly higher number of species during the second year.
Throughout the survey period, only plants in flower were identified in the vast majority of cases in order to increase the reliability of observations. The exceptions were some trial tree identifications, shrub identifications (such as the genus Nitida, Taraxacum), and Hedera helix, which is imminently recognizable and is common throughout survey locations. Note that Poaceae and Juncacea (grasses and sedges) were left off the survey entirely due to the difficulty in identification. However, the Poaceae family is clearly ubiquitous and nearly all surveys could have at least one member of the poaceae family added. For all species, the subspecies were not recorded.
The identification of a plant followed generally the following three steps:
Nearly all plants could be identified following this algorithm, which became increasingly efficient as time went on. In addition, as the number of species that fell under the first category increased the surveys became increasingly quick as well. Some direct results of this data collection protocol are the following:
Above : Some summary statistics for the first year of sampling. Note that the survey period went from June 2020 - August 2020. Note also the great increase in observations during the month of August compared to the other months.
Above : The same summary statistics for year 2. Note that the survey period begain in February rather than June and the significant increase in the number of surveys and the number of species identified.
This analysis follows the classification and definitions of Info Flora. The first major distinction is between native and non-native plants: all species that arrived after 1500 (the discovery of America) are considered non-native / non indigenous. Since native species are evaluated under the IUCN redlist, it was assumed that any species on the redlist is a native species. Aside from the quite small category of "ns" (5 observations, or .08% of all species identified) which houses non-native but culturally valuable species (such as tulips that grow in humid meadows) and the few native species not included in the IUCN red list, all species fall neatly into either (1) the native species characterized by an IUCN Redlist attribute or (2) non-native species.
Throughout the survey period most species identified were native and classified as "Least Concern", the lowest category of risk of local and global extinction, according to the latest IUCN Redlist data. This is in line with what might be expected: the survey would likely identify populations of hardy, common plants resistant to anthropogenic pressures. As can be seen in the charts below, the general proportion of the categories remains the same between the different years and across months, with some variation as will be seen in the following sections.
Top left: The number of unique species broken down per month and per classification category for 2020 surveys, Top right: The number of unique species broken down per month and per classification survey for the 2021 surveys. Bottom: The number of unique species identified per survey plotted monthly.
The vast majority of non-native plants are also not invasive and most have little to no chance of establishing spontaneous populations in the wild or in urban spaces. One example of a common non native, non-invasive plant, classified as ni in the chart below, is the annual Conyza canadensis (Erigeron canadensis) from North America that thrives in disturbed areas around the city. It was identified in 12 locations in August and September 2021, however these numbers underplay the relative amount of the plant in a given location as it spreads quickly and can dominate a given area during the late summer. Despite this dominance, the plant generally cedes its place to normal succession processes as time passes and thus is not considered invasive. Another two common examples of this category are Onobrychis viciifolia, common in fields and along road verges in late spring and early summer, and Eupatorium cannabinum, common along road verges and river banks. Both of these latter plants are available as "wild type" and are available in seed mixes for renaturalization and wildflower area creation.
Above : Three different common non-native, non-invasive plants that grow in different environments around Biel/Bienne.(Left to right) O. viciifolia is commonly found in blooms in fields, road and railroad berms in late spring; C. canadensis is an annual common in lots and highly disturbed areas; E. cannabinum thrives along river banks and in more humid areas and can bloom throught the late spring and summer.
Of all non-native species a small number are considered invasive. They must be able to reproduce in the wild and pose a threat to humans and local ecosystems. Usually for invasive plants this is through displacement of plant populations - the invasive species takes over a given area and native species have difficulty pushing it out. Info Flora maintains a list of the current watch list and black list species, a number of which were identified over the course of the survey. Some of them were purposefully planted, such as the rows of Mahonia aquifolium throughout Biel/Bienne's Madretsch quarter. Others have moved in of their own accord such as Solidago canadensis and Erigeron Annuus.
Invasive species in this study is defined as those species classified as either being on the Watch List (WL) or the Black List (BL) from the 2014 list compiled by Infoflora and the FOEN. Many more instaces of BL species were recorded than WL species throughout the course of the survey period, as can be seen in the below chart and tables. Te most important take away is that invasive species are driven by a few key species, namely Erigeron annuus (BL), Solidago canadensis (BL), Senecio inaequidens (BL), Buddleja davidii (BL) and Mahonia Aquifolium (WL), with E. annuus twice as common as its nearest competitor, S. canadensis. The most common WL species was M. aquifolium and is both very distinctive and had been widely planted by the municipality in preceeding decades.
Above : Three common species of invasive plants found throughout the city. While all three of them spring up sontaneously, M. aquifolium was planted purposefully throughout the city and dominates some areas in Madretsch, such as Kreuzplatz.
One interesting absence across all survey locations was Reynoutra japonica, a member of the Blacklist (BL). An aggressive invader of riverbanks and increasingly common throughout waterways in Switzerland, only one stand was identified near the Mettmoos park in Längholz. The following tables and charts summarize the BL and watchlist (WL) species identified over the course of the surveys. Note that Watchlist dynamics is driven by M. Aquifolium and BL dynamics are driven by a few species, but especially E. Annuus, followed by Solidago canadensis and Senecio inaequidens.
erigeron-annuus 138 solidago-canadensis 57 senecio-inaequidens 40 buddleja-davidii 25 robinia-pseudoacacia 11 prunus-laurocerasus 5 reynoutria-japonica 2 prunus-serotina 2 rubus-armeniacus 1 artemisia-verlotiorum 1 impatiens-glandulifera 1 heracleum-mantegazzianum 1 solidago-gigantea 1 Name: species, dtype: int64
mahonia-aquifolium 47 sedum-spurium 3 symphoricarpos-albus 2 parthenocissus-inserta 2 Name: species, dtype: int64
Above: The above tables of the Black List and Watch List species demonstrate that the overall abundance of invasive species in the survey locations was driven by a few key species.
The number of unique invasive species identified on the blacklist and Watchlist rose from one species each identified in February, March and April to a high of 7 species and 4 species respectively, in July. To a certain extent this is due to counting plants in flower - some early populations of Erigeron annuus were found and Mahonia aquifolium begain to flower in March and April. The higher numbers of identified species in June, July, August and September corresponds to the flowering season of E. Annuus, S. canadensis and S. inaequidens
*Top Left: The number of times an invasive speces was recorded per month in year one. Top right: The number of times an invasive speces was recorded per month in year 2. Bottom: The number of unique invasive species recorded per survey in each month. As can be seen, the peak for both years was in August.
The IUCN Red List is an internationally comparable ranking of the conservation status of individual species and biotopes. Infoflora worked with the IUCN to create a national redlist for Switzerland, last updated in 2016. This analysis was complemented in 2019 with the publishing of regional redlist report. This regional redlist data provided a IUCN redlist rating for each native species in each of Switzerland's main biogeographical regions. In the previous analysis of redlist species, the national rating was used as around 500 observations in the Jura and Northern Alps were included in the surveys. As Biel/Bienne is located on the middle plateau, this section uses only observations made within the middle plateau region and categorizes them according to this regional redlist analysis. This is still the vast majority of survey locations and species identified - about 7000 observations total.
Above : Some examples of native species found throughout Biel/Bienne. From left to right: D. Pilosella, Anemone nemorosa, Epilobium dodonaei
Above: The below chart demonstrates the key point that most species found are classified as "Least Concern" (LC). The species themselves are widespread (hence the categorization of LC) and the surveys were conducted in disturbed, urban environments where one is unlikely to find rare species.
As noted in the introduction, the regional redlist for the central plateau ranks many species on a higher risk classification than the national redlist as many populations are under more threat on the central plateau than in other biogeographic regions. While species in each category were identified, the vast majority of native species were of least concern. Compared to using the national redlist ranking, the overall results do not change much, with only a few species moving from Least Concern to Near Threatened.
To put the observations in context, according to Infoflora, 1207 different vascular plant species were identified in the 100 square kilometers roughly centered on Biel/Bienne. Of these species, some 750 were not identified on the plant surveys and about 100 species were identified in the surveys but not included in Infoflora's list of observations. While a great part of this mismatch is due to the surveyor not identifying most trees and grasses, it also indicates a significant floral diversity in the region that was not identified in the surveys. It also indicates that Infoflora may be underestimating the diversity of plant species in urban spaces, even if this diversity comes from commercial seeds and non-native plants.
Some general conclusions that can be drawn from the data are the following:
Plant surveys need to be done systematically and year on year as weather and other random factors significantly affect the population distributions of vascular plant species. The first survey year, 2020, coincided with the warmest year on record in Switzerland, tied with 2018, with a scarcity of rainfall. Meanwhile, 2021 saw the wettest and coldest spring and summer weather for many local records. It is thus to be expected that these extreme variations would result in different plant species being identified across Biel/Bienne as a whole and even in certain survey locations. One anecdote of this is a regionally Near Threatened species, Dipsacus pilosus, which was identified near the Ile de la Suze on the banks of the Suze river in 2020, however in 2021 the site was submerged for much of the survey period due to the extra rainfall and there was no sign of its presence. While this sort of data can begin to be teased out by comparing the roughly 50 sites that overlap between 2020 and 21, the overall year on year analysis should wait until the 2022 data can be gathered.
The microlevel nature of these surveys allows for a neighborhood by neighborhood and block by block analysis of plant resources in the city. Similarly, features such as road verges, rail road berms, and parks can be compared across the city. Some of this analysis will be done in a separate notebook for the 2021 data using some features already keyed to the observations. In addition, there are clear and direct extensions thanks to rich sources of data available from municipal authorities that could allow explanatory causes to be determined and differentiated site treatments to be evaluated. One example that will be addressed is that ProNature grazes sheep on select railroad berms - are there differentiated levels of diversity in these locations compared to surrounding non-treated sites? The additional data that should be explored is the following:
In short, there are a number of interesting extensions to this analysis, some of which are possible with the available data and some of which will require integration with other datasets or collection of additional data. Plant surveys will begin anew in mid February 2022. Due to the surveyor's experience, it is expected to match or exceed the observations made in 2021, which will provide a strong year on year data set of species make-up in different locations.
The surveys will be repeated in year 3. Given the surveyor's additional experience with the subject matter, it is expected to collect significantly more observations and to continue to improve accuracy, efficiency, and geographic coverage. This increased data will also be relatively easier thanks to experience working with the data and having prewritten useful code for its analysis and visualization.
The objective of year three is to build the predictive capacity of the data set to answer the following questions: Given the list of vascular plant species that occur in this area and this set of environmental data, what can I predict about the supported biodiversity ? What areas are most important for target species (bees/butterflies) throughout the year ?
This will require collecting plant occurence data on a wide array of habitats throughout the year and integrating this data into a format compatible for analysis with satellite and GIS data from the municipalaity. In additon
Surveys will be conducted from February through September 2022. This is to capture the early and late blooming flowers that are especially important for hibernating insect species. Ideally each location will be surveyed on a bi-monthly basis to capture the seasonality of the flowering populations, but this will likely not be a possible schedule to maintain for all observation. Thus, a core group of locations will receive this treatment, while other locations will be surveyed opportunistically with the aim of establishing a solid coverage of the municipality of Biel/Bienne. The surveys will again be focused on Biel and the immediate surrounding periurban region. The same locations will be surveyed as in 2021 with some geographic expansion.
The surveys will be conducted using the infoflora app on an android smartphone (Samsung A51). Surveys will again be focused on identification of species and not an estimation of ground cover or dominance. The following differences will be registered:
A major focus of year three is the compatibility of this data set with the needs of the municipal, cantonal and federal managers of green spaces and biodiversity. As such, a more active approach to the integration of data from Infoflora, the municipality of Biel/Bienna and surrounding communes. In addition, in order to investigate the results of interventions that have taken place over the years, data will be sought out on renaturalization projects to attempt to identify outcomes.
Currently enrolled as a master student at the Oeschger Center for Climate Change Research at the Universität Bern, these surveys will serve as the foundation for my thesis work on (sub)urban plant populations in times of significant climate change. Previously trained as an economist these surveys have also been an avenue to quickly developy my knowledge of the local flora, culminating in receiving the first-level accreditation, Bellis certificate, from the Swiss Botanical Society in 2021.
Qustions ? Comments ? Feedback most welcome at thor.erismann @ gmail.com